If these are layers and not meat birds, then you can safely offer free choice 24/7 to them. Chickens will self regulate their own calorie needs and thus intake. If on the other hand you have more birds than you can feed… you might be best advised to reduce the bird count until you reach a point you are comfortable with. If you can let them out of the coop and or run and free range some, that will certainly help. Table scraps are ok in moderation, but you should be offering a complete ration that has all of the vitamins and trace minerals, if these are in short supply the birds will try to compensate with what ever they 'can' find to eat.
Best to you and your birds,
RJ